This invention relates generally to integrated gasification combined-cycle (IGCC) power generation systems, and more specifically to improving gasifier performance using partial moderator bypass.
At least some known IGCC systems include a gasification system that is integrated with at least one power producing turbine system. For example, known gasifiers convert a mixture of fuel, air or oxygen, steam, and/or limestone into an output of partially oxidized gas, sometimes referred to as “syngas.” The syngas is supplied to the combustor of a gas turbine engine, which powers a generator that supplies electrical power to a power grid. Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator that generates steam for driving a steam turbine. Power generated by the steam turbine also drives an electrical generator that provides electrical power to the power grid.
To achieve a pumpable slurry concentration, at least some know gasification systems feed excess water moderator to the gasifier. Excess water moderator is also used where a high hydrogen content syngas is desirable. In addition, recycle CO2 to the gasifier is also used for IGCC to increase CO content (syngas lower heating value (LHV)) and carbon conversion. However, this excess moderator can cool the syngas below the slag fusion point resulting in higher than optimal oxygen consumption, and decreased syngas production.